CN119517708A

CN119517708A - Indirectly heated cathode ion source and target holder

Info

Publication number: CN119517708A
Application number: CN202411626939.9A
Authority: CN
Inventors: 沙颜士·P·佩特尔; 格拉汉·莱特; 丹尼尔·艾凡瑞朵; 丹尼尔·R·泰格尔; 布賴恩·S·高里; 小威廉·R·伯吉阿哥斯; 本杰明·奥斯瓦尔德; 奎格·R·钱尼
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2019-10-09
Filing date: 2020-09-15
Publication date: 2025-02-25
Also published as: US20210375585A1; WO2021071634A1; US20210110995A1; US11664192B2; TW202129677A; TWI858645B; KR20240170578A; KR20220071252A; KR102734100B1; US20230260745A1; CN114514593A; JP2024054135A; CN114514593B; JP7423763B2; TWI801755B; US11170973B2; JP2022552182A; JP7618853B2; TW202331764A

Abstract

The invention discloses an ion source for accommodating a target seat of a solid doping material, in particular an indirect heating cathode ion source and the target seat. The ion source includes a thermocouple disposed proximate the target mount to monitor the temperature of the solid state dopant material. In certain embodiments, the controller uses this temperature information to alter one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the position of the target in the arc chamber. Various embodiments are shown showing the connection between the controller and the thermocouple. In addition, embodiments are presented that illustrate various placements of thermocouples on the target.

Description

Indirect heating type cathode ion source and target seat

The invention relates to a divisional application of an invention patent application with the application number 202080070072.7 and the invention name of indirect heating type cathode ion source and target seat, which is put forward by 9/15/2020.

Technical Field

Embodiments of the present disclosure relate to an indirectly heated cathode ion source and target, and more particularly to an ion source having an insertable target for receiving a solid dopant material, wherein the temperature of the dopant material or target may be measured and optionally controlled.

Background

Various types of ion sources may be used to form ions for use in semiconductor processing equipment. For example, an Indirectly Heated Cathode (IHC) ion source operates by supplying current to filaments disposed behind the cathode. The filaments emit thermionic electrons that accelerate toward and heat the cathode, which in turn causes the cathode to emit electrons into an arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller may be disposed at an end of the arc chamber opposite the cathode. The cathode and repeller may be biased to repel electrons, directing them back toward the center of the arc chamber. In some embodiments, a magnetic field is used to further confine electrons within the arc chamber. Multiple sides are used to connect the ends of the arc chamber.

An extraction aperture is provided along one of these sides near the centre of the arc chamber through which ions formed in the arc chamber can be extracted.

In certain embodiments, it may be desirable to utilize a material in solid form as the dopant species. For example, a crucible or a target may be used to contain the metal such that when the metal liquefies, the liquefied metal remains in the target. The use of pure solid metal directly for ion implantation can increase the beam current available for wafer implantation.

However, there may be problems associated with using a target for solid state doping materials. For example, when metals with low melting and low boiling temperatures are used in a carrier target, extremely high temperatures can be problematic. For example, the dopant material may become unstable and be prone to out-of-control effects that may cause inconsistent beam performance and cause undesirable accumulation of dopant material in the arc chamber.

Thus, an ion source that can be used with solid state doping materials having low melting temperatures (e.g., certain metals) and that is capable of monitoring and controlling the internal temperature thereof would be beneficial.

Disclosure of Invention

An ion source having a target housing solid state dopant material is disclosed. The ion source includes a thermocouple disposed proximate the target mount to monitor the temperature of the solid state dopant material. In certain embodiments, the controller uses this temperature information to alter one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the position of the target in the arc chamber. Various embodiments are shown showing the connection between the controller and the thermocouple. In addition, embodiments are presented that illustrate various placements of thermocouples on the target.

According to one embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source includes an arc chamber including a plurality of walls connecting a first end and a second end, an indirectly heated cathode disposed on the first end of the arc chamber, a target having a pocket for containing a dopant material, a thermocouple in contact with the target, and a controller in communication with the thermocouple, wherein the controller alters a parameter of the ion source based on a temperature measured by the thermocouple. In certain embodiments, the ion source further comprises an actuator in communication with the target to move the target between a first position and a second position, and wherein the parameter comprises a position of the target. In some embodiments, the parameter is selected from the group consisting of arc voltage, filament current, cathode bias voltage, flow rate of the feedstock gas, and beam extraction current. In certain embodiments, the ion source further comprises a heating element in communication with the target, and wherein the parameter comprises a current supplied to the heating element. In some embodiments, the ion source further comprises an actuator assembly comprising a wire for electrically connecting the thermocouple to the controller, a housing comprising a rear housing, a front housing, and an outer housing connecting the rear housing and the front housing, a shaft affixed to the target mount and having a retaining plate disposed within the housing, a bellows disposed within the housing and affixed to the retaining plate on one end and affixed to the rear housing on an opposite end, and an actuator for linearly translating the shaft. In some embodiments, a connector is mounted in the front housing and the wire passes from the controller through a space between the outer housing and the bellows and terminates at the connector. In some other embodiments, a second connector is mated to the connector, and a thermocouple wire is disposed between the second connector and the thermocouple. In some embodiments, the thermocouple wires are coiled to enable adjustment of the position of the target relative to the arc chamber. In some embodiments, the thermocouple wires are packaged in a inconel braid (Inconel braid). In some embodiments, the thermocouple wires are packaged in an alumina tube. In certain embodiments, the lead passes through the hollow interior of the shaft. In certain embodiments, the target holder comprises a target base, a crucible plug, a crucible, and a porous plug. In some embodiments, the thermocouple is disposed on an outer surface of the crucible. In certain embodiments, a cavity is provided on an inner surface of the target mount, and the thermocouple is provided in the cavity on an outer surface of the crucible plug. In some embodiments, potting material is used to hold the thermocouple in place. In some embodiments, set screws are used to hold the thermocouple in place. In some embodiments, a spring is provided in the cavity to hold the thermocouple in place. in some embodiments, the ion source comprises a heating element in communication with the target, wherein the heating element comprises a resistive wire. In certain embodiments, the resistive wire is in communication with the crucible or the crucible plug.

In accordance with another embodiment, an assembly for use with an ion source is disclosed. The assembly comprises a connecting piece, a thermocouple and a wire, wherein the wire is arranged between the connecting piece and the thermocouple. In certain embodiments, the wire is coiled. In certain embodiments, the wires are individually insulated. In some embodiments, the insulated wire is wrapped in a inconel braid. In certain embodiments, the insulated wire is packaged in an alumina tube.

According to another embodiment, a target for use in an ion source containing a dopant material is disclosed. The target holder includes a target base, a crucible shaped as a hollow cylinder, a crucible plug covering one open end of the crucible and disposed proximate the target base, a porous plug covering an opposite end of the crucible through which gaseous dopant material may pass, and a thermocouple in communication with the target holder. In certain embodiments, a thermocouple is disposed on an outer surface of the crucible. In other embodiments, the thermocouple is disposed in a channel in the wall of the crucible. In some embodiments, a cavity is disposed in the target base proximate the crucible plug, and the thermocouple is disposed in the cavity proximate the crucible plug. In certain embodiments, a channel is provided in the target base, wherein the channel communicates with the cavity to enable the laying of wires to the thermocouple. In some embodiments, potting material is used to hold the thermocouple in place. In certain embodiments, set screws are used to hold the thermocouple in place. In some embodiments, the target mount includes a shaft affixed to the target base. In a certain embodiment, the interior of the shaft is hollow to enable a wire to be routed through the hollow interior of the shaft to the thermocouple.

According to another embodiment, an indirectly heated cathode ion source is disclosed. The ion source includes an arc chamber including a plurality of walls connecting a first end and a second end, an indirectly heated cathode disposed on the first end of the arc chamber, a target having a pocket for containing a dopant material, wherein the target is movable within the arc chamber, and a controller, wherein the controller alters a position of the target within the arc chamber based on a temperature of the dopant material. In some embodiments, the temperature of the dopant material is determined using an optical measurement, pyrometer, color point, thermocouple, wireless thermocouple reader, or resistance temperature detector (RESISTANCE TEMPERATURE DETECTOR, RTD). In certain embodiments, a thermocouple is used to determine the temperature of the dopant material. In some embodiments, the temperature of the dopant material is estimated based on a temperature of a component within the arc chamber.

Drawings

For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference and in which:

Fig. 1 is an Indirectly Heated Cathode (IHC) ion source with an insertable target in accordance with one embodiment.

Fig. 2 illustrates an actuator assembly and a target in accordance with one embodiment.

Fig. 3 shows an actuator assembly and a target according to a second embodiment.

Fig. 4 shows an actuator assembly and a target according to a third embodiment.

Fig. 5 illustrates placement of a thermocouple on a target in accordance with one embodiment.

Fig. 6 shows placement of a thermocouple on a target according to a second embodiment.

Fig. 7 illustrates placement of a thermocouple on a target mount according to another embodiment.

Fig. 8A-8B illustrate placement of a thermocouple on a target in accordance with other embodiments.

Fig. 9A-9C illustrate placement of a thermocouple on a target in accordance with other embodiments.

Fig. 10 illustrates an actuator assembly and a target according to one embodiment in which resistive wires are used to heat the target.

Detailed Description

As described above, at extremely high temperatures, solid dopants in the ion source may melt too fast and form undesirable dopant accumulation in the arc chamber. At low temperatures, the solid dopant may not melt at all.

Fig. 1 shows an IHC ion source 10 with a target mount, which IHC ion source 10 overcomes these problems. The IHC ion source 10 includes an arc chamber 100, the arc chamber 100 including opposite ends and a wall 101 connected to the ends. The walls 101 of the arc chamber 100 may be constructed of a conductive material and may be in electrical communication with each other. In some embodiments, a liner may be provided proximate one or more of the walls 101. A cathode 110 is disposed in the arc chamber 100 at the first end 104 of the arc chamber 100. The filament 160 is disposed behind the cathode 110. Filament 160 is in communication with filament power supply 165. Filament power supply 165 is configured to pass an electrical current through filament 160 such that filament 160 emits thermionic electrons. The cathode bias power supply 115 negatively biases the filament 160 with respect to the cathode 110 to accelerate the thermionic electrons from the filament 160 toward the cathode 110 and to heat the cathode 110 as the thermionic ions strike the rear surface of the cathode 110. The cathode bias power supply 115 may bias the filament 160 such that the filament 160 has a voltage, for example, between 200V and 1500V minus the voltage of the cathode 110. The voltage difference between cathode 110 and filament 160 may be referred to as a cathode bias voltage. Then, the cathode 110 emits thermionic electrons into the arc chamber 100 on its front surface.

Thus, filament power supply 165 supplies current to filament 160. The cathode bias power supply 115 biases the filament 160 such that the filament 160 has a more negative value than the cathode 110, thereby drawing electrons from the filament 160 toward the cathode 110. In some embodiments, the cathode 110 may be biased relative to the arc chamber 100, for example, by a bias power supply 111. The voltage difference between the arc chamber 100 and the cathode 110 may be referred to as an arc voltage. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the bias power source 111 may not be employed and the cathode 110 may be electrically connected to the wall 101 of the arc chamber 100. In certain embodiments, the arc chamber 100 is connected to electrical ground.

A repeller 120 may be disposed on the second end 105 opposite the first end 104. The repeller 120 may be biased relative to the arc chamber 100 by a repeller bias power supply 123. In other embodiments, the repeller 120 may be electrically connected to the arc chamber 100 to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the repeller bias power supply 123 may not be employed and the repeller 120 may be electrically connected to the wall 101 of the arc chamber 100. In still other embodiments, the repeller 120 is not employed.

The cathode 110 and the repeller 120 are each made of a conductive material (e.g., metal or graphite).

In certain embodiments, a magnetic field is generated in the arc chamber 100. This magnetic field is intended to confine electrons in one direction. The magnetic field is generally parallel to the wall 101 from the first end 104 to the second end 105. For example, electrons may be confined in columns parallel to the direction from the cathode 110 to the repeller 120 (i.e., the Y direction). Therefore, the electrons do not undergo any electromagnetic force and move in the Y direction. However, movement of electrons in other directions may be subject to electromagnetic forces.

Extraction apertures 140 may be provided on one side of the arc chamber 100, said one side of the arc chamber 100 being referred to as extraction plate 103. In fig. 1, the extraction aperture 140 is disposed on a side parallel to the Y-Z plane (perpendicular to the page). In addition, the IHC ion source 10 also includes a gas inlet 106 through which gas 106 a gas to be ionized can be introduced into the arc chamber 100.

In certain embodiments, the first and second electrodes may be disposed on respective opposing walls 101 of the arc chamber 100 such that the first and second electrodes are located within the arc chamber 100 on the wall adjacent to the extraction plate 103. The first electrode and the second electrode may each be biased by a respective power source. In some embodiments, the first electrode and the second electrode may be in communication with a common power source. However, in other embodiments, to enable maximum flexibility and to be able to tune the output of the IHC ion source 10, the first electrode may be in electrical communication with a first electrode power source and the second electrode may be in electrical communication with a second electrode power source.

The controller 180 may be in communication with one or more of the power sources such that the voltage or current supplied by these power sources may be altered. The controller 180 may include a processing unit, such as a microcontroller, a personal computer, a dedicated controller, or another suitable processing unit. The controller 180 may also include a non-transitory storage element, such as a semiconductor memory, a magnetic memory, or another suitable memory. Such non-transitory storage elements may contain instructions and other data that enable the controller 180 to perform the functions described herein.

The IHC ion source 10 further includes a target 190, the target 190 being insertable into the arc chamber 100 and removable from the arc chamber 100. In the embodiment of fig. 1, the target 190 enters the arc chamber along one of the walls 101 of the arc chamber 100. In certain embodiments, the target 190 may enter the arc chamber 100 at a mid-plane between the first end 104 and the second end 105. In another embodiment, the target 190 may enter the arc chamber 100 at a different point than the mid-plane. In the embodiment shown in fig. 1, the target 190 passes through the side of the arc chamber 100 opposite the extraction aperture 140. However, in other embodiments, the target 190 may enter through a side adjacent to the extraction plate 103. The target 190 is movable between a first position and a second position.

The target 190 has a cavity or pocket 191 into which the doping material 195 may be disposed. Bladder 191 may have a bottom surface and sidewalls extending upwardly from the bottom surface. In some embodiments, the sidewalls may be vertical. In other embodiments, the sidewalls may slope outwardly from the bottom surface. In some embodiments, the sidewalls meet the bottom surface at a rounded edge. The bottom surface and the side walls form a cavity closed at the bottom. In other words, much like a conventional cup, the doping material 195 is inserted or removed through the open top, and the sidewalls and bottom surface form a seal from which the doping material 195 cannot exit. In another embodiment, bladder 191 may be enclosed such that doped material 195 is disposed within bladder 191. For example, bladder 191 may be formed using a hollow cylindrical crucible. Porous plug 192 may be used to retain the doping material within bladder 191 and enable vapor to exit bladder 191. For example, the porous plug 192 may be graphite foam. The feed rate of the dopant material from the target 190 may also be controlled by adding various sized patterned holes to the porous plug 192 or adding any other walls of the target 190. Any of the walls of the target 190 may be porous material and used to control the feeding of the doping material into the arc chamber 100.

A doping material 195 (e.g., indium, aluminum, antimony, or gallium) may be disposed within the pocket 191 of the target 190. The doping material 195 may be in a solid form when placed in the bladder 191. The doping material 195 may be in the form of a block, file, chip, sphere, or in other shapes. In certain embodiments, the doping material 195 may melt and become a liquid. Thus, in certain embodiments, the target 190 is configured to enter the arc chamber 100 such that the open end face is up and the sealed bottom is facing down, such that molten dopant material 195 cannot flow from the target 190 into the arc chamber 100, but is retained in the target 190. In other words, the IHC ion source 10 and the target 190 are oriented such that the dopant material 195 is held within the capsule 191 by gravity.

The thermocouple 198 may be proximate to the target holder 190 or the doped material 195. This thermocouple 198 may be in communication with the controller 180. Thermocouple 198 may include one or more wires 199 electrically connecting thermocouple 198 to controller 180.

In some embodiments, a thermocouple 198 may be secured to the outside of the target mount 190. In other embodiments, the thermocouple 198 may include a rigid sheath that may be used for positioning relative to the target. In another embodiment, the thermocouple measurement point may be located directly within bladder 191 containing doping material 195. In these embodiments, a ceramic insulator sheath may be used to protect the thermocouple wires from corrosion of the thermocouple 198.

During operation, filament power supply 165 passes a current through filament 160, which causes filament 160 to emit thermionic electrons. These electrons strike the rear surface of the cathode 110, which may be more positive than the filaments 160, thereby causing the cathode 110 to be heated, which in turn causes the cathode 110 to emit electrons into the arc chamber 100. These electrons collide with molecules of the gas fed into the arc chamber 100 through the gas inlet 106. A carrier gas (e.g., argon) or an etching gas (e.g., fluorine) may be introduced into the arc chamber 100 through a gas inlet 106 in place. Electrons, gas, and positive potential from cathode 110 combine to form a plasma. In some embodiments, electrons and positive ions may be slightly constrained by a magnetic field. In certain embodiments, the plasma is confined adjacent the center of the arc chamber 100 and near the extraction aperture 140. Chemical etching or sputtering by plasma converts the doping material 195 into a gas phase and ionization is achieved. The ionized feedstock material may then be extracted through extraction aperture 140 and used to prepare an ion beam.

For maintaining the plasma at a more positive voltage than the target 190, thereby attracting negative ions and neutral atoms sputtered or otherwise released from the dopant material 195 toward the plasma.

In certain embodiments, the doping material 195 is heated and vaporized due to the heat of the plasma formation. However, in other embodiments, the doping material 195 may also be heated by additional means. For example, a heating element 170 may be provided within the target 190 or on the target 190 to further heat the dopant material 195. The heating element 170 may be a resistive heating element or some other type of heater.

In some embodiments, the target 190 may be made of a conductive material and may be grounded. In various embodiments, the target 190 may be made of a conductive material and may be electrically floating. In various embodiments, the target 190 may be made of a conductive material and may be maintained at the same voltage as the wall 101. In other embodiments, the target 190 may be made of an insulating material.

In yet another embodiment, the target 190 may be electrically biased with respect to the arc chamber 100. For example, the target mount 190 may be made of a conductive material and may be biased by a separate power source (not shown) to be at a different voltage than the wall 101. This voltage may have a more positive value or a more negative value than the voltage applied to the wall 101. As such, the electrical bias may be used to sputter the doping material 195.

The controller 180 may monitor the temperature of the dopant material 195 using a thermocouple 198. In certain embodiments, the controller 180 may be in communication with the thermocouple 198 and with the heating element 170. Accordingly, the controller 180 may control the heating element 170 to maintain the doping material 195 at a desired or predetermined temperature. In other words, the controller 180 may vary the current through the heating element 170 to maintain a desired temperature measured by the thermocouple 198. This may enable the controller 180 to control the feed rate of the doping material 195 into the arc chamber 100. In other embodiments, the controller 180 may indirectly measure the temperature of the doping material 195, such as by measuring the temperature of the target mount 190 or some other component.

The target 190 communicates with one end of the shaft 200. The opposite end of the shaft 200 may be in communication with an actuator assembly 300. The actuator assembly 300 may be directly attached to one of the walls 101. In other embodiments, the actuator assembly 300 may be retracted from the wall 101 to enable removal of the target 190 from the main cylinder of the arc chamber 100. Actuation of the actuator assembly 300 enables the target holder 190 to move linearly within the arc chamber 100.

FIG. 2 illustrates one embodiment of an actuator assembly 300. In this embodiment, the actuator assembly 300 includes a rear housing 310 and a front housing 340. The front housing 340 may latch or otherwise connect to one of the walls 101 of the arc chamber 100. Alternatively, the front housing 340 may be retracted from the wall 101. An outer housing 360 may be used to connect the rear housing 310 with the front housing 340.

Within the rear housing 310 is an actuator 320. The actuator 320 may have a drive shaft 325. In some embodiments, the actuator 320 is an electric motor, although other types of actuators may be used. In one embodiment, the drive shaft 325 has a threaded distal end 326. A corresponding threaded member 330 may be in communication with threaded distal end 326. Threaded member 330 may be affixed to shaft 200. As such, when the drive shaft 325 rotates, the threaded member 330 is pulled to the actuator 320 or the threaded member 330 is moved away from the actuator 320 depending on the direction of rotation. Since the shaft 200 is affixed to the threaded member 330, rotational movement of the drive shaft 325 similarly translates the shaft 200 linearly in the X-direction. This allows target holder 190 to be positioned in different locations within arc chamber 100.

In this embodiment, the shaft 200 includes a retaining plate 210. The retention plate 210 is disposed within the actuator assembly 300 rearward of the front housing 340. The retainer plate 210 is welded or otherwise connected to the bellows 350. In some embodiments, the bellows 350 may be metal. The bellows 350 may also be welded or otherwise attached to the rear housing 310. The bellows 350 and the holding plate 210 form a barrier between the vacuum conditions in the arc chamber 100 and the atmospheric conditions side outside the arc chamber 100. Accordingly, when the drive shaft 325 rotates, the bellows 350 expands and contracts based on the direction of movement of the shaft 200.

Note that thermocouple 198 is disposed within arc chamber 100 and requires wire 199 to exit arc chamber 100 while maintaining the integrity of the vacuum conditions. In the embodiment of fig. 2, the first connector 390 is mounted within the arc chamber 100 on the front housing 340. The wire 199 extends from outside the actuator assembly 300 to the first connector 390. In this embodiment, a passage 311 may be formed in the rear housing 310 to enable the wire 199 to pass out of the actuator assembly 300. The lead 199 may then be routed in the space between the bellows 350 and the outer housing 360. This space is part of the vacuum environment and thus vacuum feed-through 370 is used to maintain vacuum. A vacuum feedthrough is a means to enable the wire 199 to pass through but maintain a pressure differential between the sides of the feedthrough. Thus, the wire 199 passes through the channel 311 in the rear housing 310 and then through the vacuum feedthrough 370. The wire 199 then passes through the space between the outer housing 360 and the bellows 350 and terminates last at the first connector 390.

The second connector 391 mates with the first connector 390. Thermocouple wires 197 extend from the second connector 391 to the thermocouple 198. Thermocouple 198 may be a type K thermocouple. Further, thermocouple wires 197 attached to thermocouples 198 may be insulated. For example, in one embodiment, each of the two thermocouple wires 197 is individually coated with an insulating material. The two thermocouple wires 197 may then be wound together in a inconel braid. In other words, thermocouple wires 197 are individually coated to achieve electrical insulation and then thermocouple wires 197 are wound in pairs to protect them from the harsh environment in arc chamber 100. In another embodiment, thermocouple wires 197 may be packaged in an alumina tube.

In certain embodiments, thermocouple wires 197 are coiled, as shown in fig. 2. As such, when the target holder 190 is extended and removed, the thermocouple wires 197 are coiled and uncoiled to compensate for the change in length.

In one embodiment, thermocouple 198, thermocouple wire 197, and second connector 391 may be replaceable components. Furthermore, as described above, thermocouple wires 197 may be individually insulated in this embodiment and then wound in a braid. Further, thermocouple wires 197 may be coiled to enable length changes without kinking or interference.

The heating element 170 may be disposed within the target 190 or on the target 190 to further heat the dopant material 195. In certain embodiments, the wires associated with the heating element 170 are laid along with thermocouple wires 197.

The thermocouple 198 may be attached to the target mount 190 in a variety of ways, which are described below.

Fig. 3 illustrates a second embodiment of an actuator assembly 300. Many of the components are identical to those shown in fig. 2 and have been given identical reference designators. In this embodiment, the shaft 200 may be hollow so that thermocouple wires 197 may be routed through the interior of the shaft 200. The shaft 200 also has an opening 201 to the hollow interior. The opening 201 may be located on a side of the holding plate 210 remote from the target seat 190. As such, the opening 201 is in atmospheric conditions. If the thermocouple 198 is located within the hollow interior of the shaft 200, a vacuum feedthrough may not be required. However, if the thermocouple 198 is located on an outer surface of the target mount 190 (e.g., as shown in fig. 4), a vacuum feedthrough 370 may be used to maintain a vacuum within the arc chamber 100. The vacuum feedthrough 370 will be provided at an inlet to the hollow interior of the shaft 200.

Thermocouple wires 197 pass through the opening 201 and can exit through a channel 311 in the rear housing 310. In certain embodiments, one or more cable standoffs 351 may be used to hold thermocouple wires 197 in place. In some embodiments, the lead 199 in communication with the controller 180 is the same as the thermocouple lead 197 through the hollow interior of the shaft 200. In other embodiments, a connection may be provided between the thermocouple 198 and the controller 180 to form two separate wire segments. For example, the portion of the thermocouple wires exposed to the plasma may need to be replaced more often. Thus, this segment of wire can be formed as a replaceable unit by inserting a connection between the thermocouple 198 and the controller 180.

Thus, in this embodiment, the shaft has a hollow interior for routing thermocouple wires 197 from the thermocouple 198 to the interior of the actuator assembly 300. As noted, if the thermocouple 198 is placed under vacuum, a vacuum feedthrough 370 may be employed at the inlet to the interior of the shaft 200, as shown in fig. 4.

In certain embodiments, thermocouple wires 197 are individually insulated and then wound together in inconel braid or alumina tube. In other embodiments, inconel braids are not used as the shaft 200 protects the thermocouple wires.

Fig. 2-4 illustrate several systems that may be used to route wires from the controller 180 to the thermocouple 198. Fig. 5-9C illustrate various embodiments regarding placement of a thermocouple 198 on the target 190.

Fig. 5 shows an enlarged view of the target mount 190. In certain embodiments, the target mount 190 comprises a target base 193, the target base 193 being affixed or otherwise attached to the shaft 200. The target holder 190 may also include a crucible 196. Crucible 196 contains doping material 195. In certain embodiments, crucible 196 may be made of graphite. In some embodiments, crucible 196 may be a hollow cylinder having two open ends. A crucible plug 194 may be provided between the crucible 196 and the target base 193. Crucible plug 194 is used to plug one of the open ends of crucible 196. The target base 193 can be secured to the crucible 196 using clamps 410. As described above, porous plug 192 may be used to plug the second open end of crucible 196. As described above, this porous plug 192 may be made of graphite foam or another suitable material.

In the embodiment of fig. 5, a thermocouple 198 is mounted on the outer surface of crucible 196. Potting material 400 may be used to hold thermocouple 198 in place. Thermocouple wires 197 may be routed along the outside of the target holder 190.

Fig. 6 shows another embodiment of a target holder 190. Many of the components are identical to those shown in fig. 5 and have been given identical reference designators. In this embodiment, a conduit 420 is formed in the target base 193 and optionally in the crucible plug 194. Thermocouple wires 197 pass through conduit 420 and thermocouple 198 is mounted on the outer surface of crucible 196 as in fig. 5. A potting material 400 may be used to hold the thermocouple 198 in place.

Fig. 7 shows another embodiment of a target holder 190. Many of the components are identical to those shown in fig. 6 and have been given identical reference designators. In this embodiment, rather than using potting material, set screw 430 is used to hold thermocouple 198 in place. Set screw 430 may be threaded into a threaded shallow hole in crucible 196. In some embodiments, the threaded shallow bore does not pass through the interior of crucible 196.

Note that set screw 430 may be used in conjunction with the embodiment of fig. 5. In other words, thermocouple wires 197 may be laid around the outside of the target holder 190 and secured to the crucible 196 using set screws 430.

In summary, fig. 5-7 illustrate different target holders 190 with thermocouples 198 in contact with the outer surface of crucible 196. Such thermocouple 198 may be affixed to crucible 196 using potting material 400 or set screw 430. Other fastening techniques may also be employed.

Additionally, a thermocouple 198 may be embedded in the wall of crucible 196. Fig. 8A shows an embodiment in which a channel 440 is formed in the wall of the crucible. Many of the components are identical to those shown in fig. 6 and have been given identical reference designators. Channel 440 is narrower than the width of the walls of crucible 196. A thermocouple 198 is inserted into the channel 440. A potting material (not shown) may be used to hold the thermocouple 198 in place. In this embodiment, the channel 440 may extend through the target base 193 and optionally through the crucible plug 194. In another embodiment shown in fig. 8B, channel 440 exits on the outer surface of crucible 196. In this embodiment, the channel does not extend through the target pedestal 193 or the crucible plug 194.

In another embodiment, the channel 440 may extend to the bladder 191 such that the thermocouple 198 is in physical contact with the interior of the bladder 191 and/or the doping material 195. In these embodiments, a ceramic insulator sheath may be employed to protect the thermocouple 198 and thermocouple wires 197.

The thermocouple 198 may also be in contact with the crucible plug 194, as shown in fig. 9A-9C. Many of the components are identical to those shown in fig. 6 and have been given identical reference designators. In these embodiments, a cavity 450 is provided in the target base 193. Cavity 450 provides a site where thermocouple 198 may be placed. A passage 460 is formed in the target base 193 from the outside of the target base 193 to the cavity 450. Thermocouple wires 197 enter cavity 450 via passage 460. Fig. 9A shows thermocouple 198 held in place by use of potting material 400. Fig. 9B shows thermocouple 198 held in place using set screw 430. Fig. 9C shows thermocouple 198 held in place using spring 470. Of course, other force-based means may be used to hold the thermocouple 198 in place.

While the above disclosure describes various means for routing the wires of the thermocouple 198 to the target 190, the same techniques may be used to route the resistive wires to the target 190. These resistive wires may be used as heating elements 170. For example, the resistive wire may be in contact with all or a portion of the outer surface of crucible 196, as shown in fig. 1-4. The resistive wire may be laid down using the same means as shown in figures 2 to 7. Alternatively, the resistive wire may be embedded in the wall of the crucible, similar to the embodiment shown in fig. 8A-8B. In another embodiment, the resistive wire may be in contact with a crucible plug 194, such as shown in fig. 9A-9C. When current is passed through the resistive wire, heat is generated. This may enable the controller 180 to control the temperature of the doping material 195 in another mechanism.

In some embodiments, the resistive wire is bundled with thermocouple wire 197. In these embodiments, the resistive wire is laid along with thermocouple wire 197.

In other embodiments, the resistive wires are provided in separate braids or bundles and traverse the same path as the thermocouple wires 197.

In still other embodiments, the resistive wire may be in contact with a portion of the backing plate 190 (e.g., crucible 196) and the thermocouple 198 is in contact with another portion of the backing plate 190 (e.g., crucible plug 194). Fig. 10 shows an embodiment in which the resistive wire 500 is separated from the thermocouple wire 197. This embodiment is similar to fig. 2, but includes a third connector 510 and a fourth connector 520. The third connector 510 may be mounted to the front case 340. A wire 540 is routed from the controller 180 to the third connector 510. In some embodiments, the assembly for laying wire 540 is similar to the assembly for laying wire 199. For example, the channel 311 and vacuum feedthrough 370 may be employed. The resistance wire 500 may be coiled to enable the length to be varied and may be connected to the outer surface of the crucible or the crucible plug.

Although fig. 10 shows a third connector and a fourth connector, it should be understood that the resistive wire 500 may also be laid along with the wire 199 and that larger connectors may be used.

Alternatively, resistive wire 500 may be laid through shaft 200, similar to the laying of wire 199 shown in fig. 3-4.

The above disclosure sets forth various embodiments that enable the controller 180 to use the thermocouple 198 to measure the temperature of the component (i.e., crucible plug, etc.) to monitor the temperature of the doping material 195. The controller 180 may use this information in various ways.

It may be advantageous to heat the doping material 195 to a temperature within a predetermined range. For example, at low temperatures, the dopant material 195 may not melt and thus dopant vapors cannot be released from the target 190. However, at too high a temperature, the melting rate of the dopant material may be too great. This may cause the dopant material to accumulate in the arc chamber 100. In addition, variations in melt rate can also affect beam current and other parameters.

By monitoring the temperature at the target 190 or near the target 190, the controller 180 may be able to better regulate the temperature of the doping material 195. For example, the controller 180 may monitor the temperature of the doping material 195. If the temperature is not within the predetermined range, the controller may change the current through the filament power supply 165, change the arc voltage, change the cathode bias voltage, change the rate of gas flow into the arc chamber 100, change the position of the target mount 190 in the arc chamber 100, change the beam extraction current, or a combination of these actions. In addition, if the first and second electrodes are disposed on the wall 101, the voltage applied to these electrodes may also be varied by the controller 180 based on the temperature of the doping material 195. Additionally, in embodiments employing a heater (e.g., through the use of resistive wire 500), the controller 180 may vary the current through the heater to vary the temperature of the doping material 195.

In certain embodiments, the controller 180 may move the position of the target 190 within the arc chamber 100 based on the temperature of the dopant material 195. For example, when the target 190 is disposed directly in a cylindrical region defined between the cathode 110 and the repeller 120, the target 190 may be heated to a higher temperature. To slow down the heating of the dopant material, the target 190 may be moved linearly outside of this cylindrical region. Conversely, to increase the temperature of the dopant material 195, the target 190 may be moved into this cylindrical region.

The controller 180 may employ various closed loop algorithms to determine parameters associated with the IHC ion source 10 based on the temperature obtained by the thermocouple 198.

While the above disclosure describes the use of thermocouples 198, other temperature sensors may be used. For example, optical measurement, pyrometry, and color point are all indirect methods of detecting the temperature of the target 190. Resistance Temperature Detectors (RTDs) and wireless thermocouple readers may also be employed. Accordingly, the above disclosure is not limited to the use of thermocouples.

Furthermore, while the above disclosure illustrates the thermocouple 198 in contact with the target seat 190 or the doping material 195, other embodiments may exist. For example, the thermocouple 198 (or other temperature sensor) may measure the temperature of another component within the arc chamber 100 and estimate the temperature of the dopant material based on this measured temperature. Such other components may be the walls of the arc chamber 100, the shaft 200, the repeller 120, the front housing 340, or another component.

Furthermore, the control described above may be performed using an open loop technique. For example, empirical data may be collected to determine the temperature of the dopant material based on various parameters, such as cathode bias voltage, arc voltage, feed gas flow rate, and position of the target. Empirical data may also determine the temperature of the dopant material as a function of time. Using a table or equation, the controller 180 may alter one or more of the parameters to maintain the doping material 195 within a predetermined range. For example, the controller 180 may move the target 190 over time to maintain its temperature within a desired range.

While the above disclosure describes the use of a target in an indirectly heated cathode ion source, the disclosure is not limited to this embodiment. The target holder, actuator assembly, and thermocouple may also be used in other ion sources or plasma sources, such as capacitively coupled plasma sources, inductively coupled plasma sources, bernas (Bernas) sources, or another suitable source.

The embodiments of the application described hereinabove may have many advantages. The use of pluggable targets enables the use of pure metal dopants as sputter targets in environments that exceed the melting temperature of the pure metal dopants. Traditionally, oxide/ceramic or other solid state composites are used that contain dopants with melting temperatures greater than 1200 ℃. The use of a compound containing dopants rather than pure materials severely dilutes the available dopant materials. For example, when Al ₂O₃ is used as a substitute for pure aluminum, the stoichiometry of the ceramic components not only introduces impurities into the plasma, which in turn may introduce undesirable masses coincident with the dopant of interest, but also results in lower beam currents than pure elemental targets. The use of Al ₂O₃ can also result in the production of undesirable byproducts, such as oxides and nitrides, which can deposit along the beamline and impair the operation of the ion implanter. For example, the beam optics may be chemically cleaned after using Al ₂O₃ to maintain the stability of the ion beam.

In one experiment, beam currents up to 4.7mA were achieved using pure aluminum sputter targets, while the maximum beam current achievable using Al ₂O₃ targets was less than 2mA. The use of pure metals will also increase the multi-charge beam current by 50% to 75% compared to beam current obtained from oxides/ceramics of the same metal species. By means of the pluggable container, large volumes of pure metal can be accessed when needed, and the solid target can be safely removed from the arc chamber to utilize other species.

In addition, by monitoring the temperature of the dopant material, the ion source may be controlled to ensure that the melting rate of the dopant material is within a predetermined range. In particular, without temperature control, the dopant feedstock may become unstable and be prone to out-of-control effects that may cause inconsistent beam performance and cause undesirable accumulation of dopant material in the arc chamber. Thus, temperature control can prevent an exponential increase in dopant vapor in the arc chamber. As well as enabling faster tuning of the ion source.

In addition, by monitoring the temperature of the dopant material, this information can be used during beam tuning, thus making beam performance more reliable.

The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from a reading of the foregoing description and accompanying drawings. Accordingly, these other embodiments and modifications are intended to be within the scope of this disclosure. Moreover, although the disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth above should be construed in view of the full breadth and spirit of the present invention as described herein.

Claims

1. A target holder for accommodating doping materials in an ion source, the target holder comprising:

Target base;

a crucible formed into a hollow cylinder; and

A porous plug covers an open end of the crucible, wherein a gaseous doping material can pass through the porous plug.

2. The target holder according to claim 1, further comprising a crucible plug, the crucible plug covering an opposite open end of the crucible and disposed adjacent to the target base.

3 . The target base according to claim 1 , further comprising a thermocouple, wherein the thermocouple is in communication with the target base.

4. The target holder of claim 3, wherein the thermocouple is attached to an outer surface of the crucible.

5. The target holder of claim 3, wherein the thermocouple is disposed in a channel in a wall of the crucible.

6. The target holder of claim 3, further comprising a crucible plug covering an opposite open end of the crucible and disposed proximate to the target base, wherein a cavity is disposed in the target base proximate to the crucible plug, and the thermocouple is disposed in the cavity proximate to the crucible plug.

7. The target base of claim 6, wherein a passage is provided in the target base, the passage communicating with the cavity to allow wires to be routed to the thermocouple.

8. The target mount of claim 3, further comprising a shaft affixed to the target base, wherein an interior of the shaft is hollow to allow a wire to be routed through the hollow interior of the shaft to the thermocouple.

9. The target backing of claim 1, further comprising a heating element in communication with the target backing, wherein the heating element comprises a resistive wire.

10. The target backing of claim 1, wherein the porous plug comprises graphite foam.

11. The target holder of claim 1 , further comprising a clamp, wherein the clamp secures the target holder to the crucible.

12. The target mount of claim 1, wherein the target base is attached to a shaft.

13. An indirect heating cathode ion source, comprising:

an arc chamber including a plurality of walls connecting the first end and the second end;

an indirectly heated cathode disposed on the first end of the arc chamber; and

The target seat as claimed in claim 1.

14. The indirectly heated cathode ion source of claim 13, wherein the target support is attached to a shaft.

15. The indirectly heated cathode ion source of claim 14, further comprising an actuator in communication with the target holder for moving the target holder within the arc chamber.

16. An indirect heating cathode ion source, comprising:

an indirectly heated cathode disposed on the first end of the arc chamber;

a shaft extending into the arc chamber; and

Target mount, including:

a target base attached to the shaft;

a crucible shaped as a hollow cylinder, wherein one end of the crucible is disposed adjacent to the target base; and

17. The indirectly heated cathode ion source of claim 16, further comprising a crucible plug covering an opposite open end of the crucible and disposed adjacent to the target base.

18. The indirectly heated cathode ion source of claim 16, further comprising a thermocouple in communication with the target support.

19. The indirectly heated cathode ion source of claim 18, wherein the thermocouple is attached to an outer surface of the crucible.

20. The indirectly heated cathode ion source of claim 18, wherein the thermocouple is disposed in a channel in a wall of the crucible.

21. The indirect heated cathode ion source according to claim 18, further comprising a crucible plug, which covers an opposite open end of the crucible and is arranged near the target base, wherein a cavity is arranged in the target base near the crucible plug, and the thermocouple is arranged in the cavity near the crucible plug.

22. The indirectly heated cathode ion source of claim 21, wherein a channel is provided in the target support, the channel communicating with the cavity to allow wires to be routed to the thermocouple.

23. The indirectly heated cathode ion source of claim 18, wherein the interior of the shaft is hollow to allow wires to be routed through the hollow interior of the shaft to the thermocouple.

24. The indirectly heated cathode ion source of claim 16, further comprising a heating element in communication with the target support, wherein the heating element comprises a resistive wire.

25. The indirectly heated cathode ion source of claim 16, wherein the porous plug comprises graphite foam.

26. The indirectly heated cathode ion source of claim 16, further comprising a clamp, wherein the clamp secures the target pedestal to the crucible.

27. The indirectly heated cathode ion source of claim 16, further comprising an actuator in communication with the shaft to move the target holder within the arc chamber.